Methods and apparatuses for releasing a chemical into a well bore upon command

ABSTRACT

One apparatus for releasing a chemical in a well bore includes a casing collar configured to couple to a casing string. A chemical container is disposed within the casing collar, and the casing collar is configured to release the chemical from the chemical reservoir.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to co-pending U.S. application Ser.No. 12/546,335, entitled “Methods and Apparatuses for Releasing aChemical into a Well Bore Upon Command,” filed concurrently herewith,the entire disclosure of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to well bore operations, and, moreparticularly, to methods and apparatuses for releasing a chemical into awell bore upon command.

Settable compositions such as cement slurries may be used in primarycementing operations in which pipe strings, such as casing and liners,are cemented in well bores. In performing primary cementing, a cementmay be pumped, for example, through the casing into an annulus betweenthe walls of a well bore and the casing disposed therein. The cement maybe pumped into the annulus until it reaches a predetermined height inthe well bore to provide zonal isolation. The cement may cure in theannulus, thereby forming an annular sheath of hardened cement (e.g., acement sheath) that supports and positions the pipe string in the wellbore and bonds the exterior surface of the pipe string to the walls ofthe well bore.

In many applications, it may be desirable to have a deployment means torelease one or more chemicals into the annulus between the well bore andthe casing so that the chemical need not be pumped from the surface atthe top of the well bore. Moreover, in the case of cementing operations,it may be desirable to not activate a cement composition in the annulusuntil a specific time chosen by an operator. Providing such a deploymentmeans may entail a number of complications such as complex and expensiveequipment and procedures. Therefore, it may be desirable to have methodsand apparatuses for chemical deployment that are inexpensive, notcomplex, and require minimal modification to existing procedures such ascementing procedures.

SUMMARY

The present disclosure relates to well bore operations, and, moreparticularly, to methods and apparatuses for releasing a chemical into awell bore upon command.

A method for releasing a chemical in a well bore is disclosed. In oneaspect, a casing string is provided, and the casing string includes acasing collar that includes a chemical reservoir. A fluid is introducedinto a space between an inner surface of the well bore and an outersurface of the casing string. A chemical is released from the chemicalreservoir into the fluid.

An apparatus for releasing a chemical in a well bore is disclosed. Inone aspect, the apparatus includes casing collar configured to connectto a section of a casing string. A chemical container is disposed withinthe casing collar, and the casing collar is configured to release achemical from the chemical reservoir.

A method for releasing a chemical in a well bore is disclosed. In oneaspect, an activator collar is connected between sections of a casingstring. The activator collar and the sections are positioned in a wellbore. A non-activated cementitious material is introduced into the wellbore. A chemical is released from the chemical reservoir into the wellbore.

The features and advantages of the present disclosure will be readilyapparent to those skilled in the art. While numerous changes may be madeby those skilled in the art, such changes are within the spirit of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features.

FIG. 1 illustrates a cross-sectional view of a casing string inaccordance with certain embodiments of the present disclosure.

FIGS. 2 a and 2 b illustrate cross-sectional views of casing and acasing collar in accordance with certain embodiments of the presentdisclosure.

FIG. 3 illustrates a method for bonding a well bore to a casing inaccordance with certain embodiments of the present disclosure.

FIGS. 4 a and 4 b illustrate cross-sectional views of casing and acasing collar in accordance with certain embodiments of the presentdisclosure.

FIG. 5 illustrates a cross-sectional view of a casing string inaccordance with certain embodiments of the present disclosure.

FIGS. 6 a and 6 b illustrate cross-sectional views of casing and acasing collar in accordance with certain embodiments of the presentdisclosure.

FIG. 7 illustrates a method for bonding a well bore to a casing inaccordance with certain embodiments of the present disclosure.

FIG. 8 illustrates a cross-sectional view of casing and a casing collarin accordance with certain embodiments of the present disclosure.

FIGS. 9 a and 9 b illustrate cross-sectional views of casing and acasing collar in accordance with certain embodiments of the presentdisclosure.

FIGS. 10 a and 10 b illustrate side and axial views of a centralizer inaccordance with certain embodiments of the present disclosure.

FIG. 11 illustrates a cross-sectional view of casing and a centralizerin accordance with certain embodiments of the present disclosure.

FIG. 12 illustrates a cross-sectional view of casing and a centralizerin accordance with certain embodiments of the present disclosure.

FIG. 13 illustrates a cross-sectional view of casing and a centralizerin accordance with certain embodiments of the present disclosure.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present disclosure relates to well bore operations, and, moreparticularly, to methods and apparatuses for releasing a chemical into awell bore upon command. Stated otherwise, the present disclosure mayallow an operator to choose a specific time at which one or morechemicals may be released into an annulus. In certain embodiments of thepresent disclosure, the subterranean well fluids useful in the presentdisclosure may be permitted to remain in a slurry state for a desiredtime before being activated through the addition of an activatorreleased from an improved casing string.

One application of the present disclosure relates to well bore cementingoperations. Typically, a cementing operation involves introducing acasing string into a well bore. A cement composition may then be pumpeddown the interior of the casing string, with a bottom plug and a topplug installed so that a cement column may be placed in between theplugs. A displacement fluid may push the cement column and plugs downthe well bore. The bottom plug may then be landed and pump pressure maycause a frangible element within the bottom plug to rupture, allowingthe cement in the casing to be pumped through the bottom plug and afloat shoe, and then up into the annular space between the casing andthe well bore. When all the cement has been pumped through the bottomplug the top plug may land on the bottom plug. As an alternative to theabove cementing operation, cement may be placed into the annulus by whatis known in the art as a reverse cementing operation. In either case, asthe placed cement sets, it bonds the casing string to a portion of thesubterranean formation.

In certain embodiments of the present disclosure, a cementitiousmaterial placed in the annulus may be non-activated. Thereafter, anoperator may initiate the setting of the cementitious material“on-command” by choosing a specific time at which to release anactivation agent into the non-activated cementitious material. Themoment of initiation may be chosen any time after cementitious materialis in place within the well bore.

A wide variety of fluids may be useful with the methods of the presentdisclosure. One of ordinary skill in the art, with the benefit of thisdisclosure, will be able to identify a suitable fluid for use in themethods of the present disclosure. In certain embodiments, thesubterranean well fluids used in the present disclosure include ahydraulic cement. A variety of hydraulic cements may be suitable for useincluding those comprising calcium, aluminum, silicon, oxygen, and/orsulfur, which may set and harden by reaction with water. Such hydrauliccements include, but are not limited to, Portland cements, pozzolaniccements, gypsum cements, high alumina content cements, silica cements,and high alkalinity cements. Cementitious material comprising shale orblast furnace slag, fly ashes, and fumed silica also may be suitable foruse in the present disclosure. In certain embodiments, the shale mayinclude vitrified shale; in certain other embodiments, the shale mayinclude raw, unfired shale, or a mixture of raw shale and vitrifiedshale.

In certain embodiments, cement hydration may be activated withconventional cement accelerators. The activator may include but is notlimited to sodium hydroxide, sodium carbonate, amine compounds, saltscomprising calcium, sodium, magnesium, aluminum, and/or mixturesthereof. One of ordinary skill in the art, with the benefit of thisdisclosure, will be able to identify a suitable activating material toaccelerate the setting of a cement slurry. In some embodiments, theactivator may comprise a calcium salt such as calcium chloride. In someembodiments, the activator may comprise a sodium salt such as sodiumchloride, sodium aluminate, and/or sodium silicate. In some embodiments,the activator may comprise a magnesium salt such as magnesium chloride.In some embodiments, the activator may comprise amine compounds such astriethanol amine, tripropanol amine, tri-isopropanol amine, and/ordiethanol amine. In some embodiments, the activator will be released ina sufficient amount to set the cement within about 1 minute to about 24hours. In embodiments including sodium chloride as the releasedactivator, the concentration may be in the range of from about 3% toabout 15% by weight of the cement in the cement slurry. In embodimentsincluding calcium chloride as the released activator, the concentrationmay be in the range of from about 0.5% to about 5% by weight of thecement in the cement slurry.

In some embodiments, the activator may “flash-set” the cement slurry. Asreferred to herein, the term “flash-set” will be understood to mean theinitiation of setting of the cement slurry within about 1 minute toabout 15 minutes after contacting the released activator. In someembodiments, the previously identified activators may flash set thecement slurry. Flash-set activators may include sodium hydroxide, sodiumcarbonate, potassium carbonate, bicarbonate salts of sodium orpotassium, sodium silicate salts, sodium aluminate salts, ferrous andferric salts (e.g., ferric chloride and ferric sulfate), polyacrylicacid salts, and/or others. In some embodiments, the following activatorscan flash-set the cement slurry based on these activators exceeding aspecified concentration: calcium nitrate, calcium acetate, calciumchloride, and/or calcium nitrite.

In alternative embodiments, a strongly-retarded cement may be activatedby degrading the retarder with an oxidizing agent. Suitable oxidizingagents may be either inorganic (e.g., sodium persulfate, sodium bromate,sodium chlorate) or organic (e.g., di-t-butyl peroxide, dicumylperoxide, t-butyl hydroperoxide), depending on the temperature and typeof retarder used. Any suitable activation system which may be deployedin the manner described herein may be used.

FIG. 1 shows cross-sectional view of an exemplary embodiment of casingstring 100 inserted into well bore 110 after well bore 110 has beendrilled to a desired depth below the surface into subterranean formation120. Annulus 130 may be formed between casing string 100 andsubterranean formation 120. Casing string 100 may include a series ofinterconnected sections of casing 140. These sections of casing 140 maybe connected by activation collars 150. Activation collars 150 may beplaced in casing string 100 and cemented in a manner similar to thatused with standard casing collars. A casing collar may be configured tobe an activation collar 150. Casing string 100 may be positioned in thewell bore with activation collars 150 installed between sections ofcasing 140 at all connections of sections of casing 140. Alternatively,activation collars 150 may be used at one or more selected locations incasing string 100 which may correspond to specific well bore locationsin the well once the entire casing string 100 to be cemented has beeninstalled.

When a non-activated cementitious material is placed within a length ofannulus 130, a non-activated condition may be maintained for a longperiod of time with no setting of the material. If complications areencountered in completing cementing operations, there may be no dangerof the cement setting during this non-activated condition, therebypossibly eliminating major remediation or causing loss of the well dueto having hardened cement where it is not desired. Once an operatordecides to “activate” the cementitious material to cause it to set, orotherwise release a chemical into the annulus, additional pressure maybe applied to displacement fluid within casing string 100. Theadditional pressure may be communicated to an activation collar 150.Activation collar 150 may be configured to release one or more chemicalsin response to a pressure increase in the casing string 100. Tofacilitate chemical dispersion, casing string 100 may be rotated and/orreciprocated axially along well bore 110. The rotation and/orreciprocation may be concurrent with, or subsequent to, the chemicalrelease.

FIG. 2 a illustrates a cross-sectional view showing details of anexemplary activation collar 200, corresponding to activation collars 150in FIG. 1, before operation. Activation collar 200 may include a hollow,generally cylindrically shaped housing 210. Generally, the activationcollars disclosed herein may be manufactured, depending upon theparticular use, from a variety of materials used for conventional casingcollars, including, but not limited to, ferrous materials, aluminum,titanium, and/or fiberglass.

Activation collar 200 may further include collar threading on one ormore surfaces of housing 210 as means of connecting to casing threadingof sections of casing 220. It should be understood by those skilled inthe art that, in certain embodiments of the present disclosure,alternative means of connecting to sections of casing 220 may beemployed. Generally, conventional sections of casing disclosed herein,depending upon the particular use, may be manufactured from a variety ofmaterials, including, but not limited to, ferrous materials, aluminum,titanium, and/or fiberglass.

Housing 210 may include one or more rupture elements 230. Ruptureelement 230 may be, for example, a rupture disk or other frangibleelement configured to mechanically break down or otherwise allow fluidcommunication in response to a given pressure on an interior surface ofhousing 210. Rupture element 230 may be configured to rupture at apredetermined pressure.

Housing 210 may further include one or more pistons 240, one or morechemical reservoirs 250, and one or more outlets 260. One or morepistons 240 may be moveable and configured to compress the volume of thechemical reservoir 250 in response to pressure communicated from theinterior of housing 210. Chemical reservoir 250 may be any suitablecontainment of an activation agent. An outlet 260 may be an open portbetween the chemical reservoir 250 and the exterior of housing 210.Outlet 260 may be appropriately sized such that the pressure balanceassociated with the exterior of housing 210 prevents the activationagent from exiting the chemical reservoir 250 until piston 240 decreasesthe volume of chemical reservoir 250 or until its volume is otherwisereduced. Alternatively, outlet 260 may include another sealing element,a wax-like substance, for example, to prevent the activation agent fromexiting the chemical reservoir 250 until piston 240 has sufficientlycompressed chemical reservoir 250. One of ordinary skill in the art,having the benefit of this disclosure, would understand that a number ofsubstantially equivalent variations of pistons 240, chemical reservoirs250, and outlets 260 may be employed and which are within the spirit ofthe present disclosure.

FIG. 2 b illustrates a cross-sectional view showing details of exemplaryactivation collar 200 after rupture element 230 has allowed fluidcommunication between the interior of housing 210 and piston 240. Piston240 is shown as having compressed chemical reservoir 250, afteractivation agent 270 has been expressed through outlet 260 into theannulus. Subsequent or simultaneous rotation and/or reciprocation of thecasing string may be used to distribute the activation agent 270 withinthe fluid in the annulus. Activation collar 200 may also be configuredto meter out activation agent 270 slowly, or at any predetermined rate.To facilitate distribution, the casing string may be rotated and/orreciprocated while and/or after the activation agent is released. Thecasing string may then be positioned in its final desired locationbefore the activator causes the cement to set.

FIG. 3 is a process flow diagram for an exemplary activation collarrunning procedure 300. In step 310, activation collars may be installedon standard casing, or collars may be installed between standard casingjoints, prior to introduction of a cementitious material into the wellbore. In step 320, the casing string may be placed into the well bore.In step 330, the cement may be pumped according to standard procedures.In step 340, the top plug may be slowly seated while pumping the cement.In step 350, sufficient rupture pressure on top plug may be provided sothat the collars may be activated before plug rupture occurs. In step360, pressure on the casing may be increased to a level sufficient toactivate collars and deploy the activation chemicals. In step 370, thecasing string may be reciprocated and/or rotated to mix the activatorwithin the cement slurry. In step 380, the casing string may bepositioned and maintained at a desired depth until cement hardening.

FIGS. 4 a and 4 b show details of another embodiment of the presentdisclosure. FIG. 4 a illustrates a cross-sectional view showing anexemplary activation collar 400 before activation agent 450 has beenexpressed through outlet 460 into the annulus. As an alternative to arupture disk, activation collar 400 may include a tension sleeve 430that holds two expelling pistons 440 together. When a pressuredifference between the interior and the exterior of the casingsufficiently increases, the tensile strength of tension sleeve 430 maybe exceeded so that it will break, thereby allowing pistons 440 to forceactivation agent 450 through port 460 and to the exterior of housing410. FIG. 4 b illustrates activation collar 400 after tension sleeve 430has given way and allowed activation agent to be expressed throughoutlet 460 into the annulus.

Thus, in accordance with certain embodiments of the present disclosure,point-distributed activation collars and methods are provided where“doses” of one or more chemicals and/or an activation agent may beintroduced at one or more points along a casing string. If necessary,the casing string may be reciprocated and/or rotated to facilitatemixing an activation agent with a fluid in the annulus. Certainembodiments of this invention may eliminate the need for external orinternal attachments to a casing string for deployment of an activationagent. Certain embodiments allow for activator distribution within anentire cross-section of an annulus. The equipment and procedures forcertain embodiments are not complex, require minimal modification toexisting cementing procedures, and have low operating risks.

FIG. 5 illustrates a cross-sectional view showing another embodiment ofthe invention. Casing string 500 may be inserted into well bore 510after well bore 510 has been drilled. Annulus 530 may be formed betweencasing string 500 and subterranean formation 520. Casing string 500 mayinclude a series of interconnected sections of casing 540. Thesesections of casing 540 may be connected by activation collars 550.Activation collars 550 may be placed in casing string 500 to be cementedin a manner similar to how standard casing collars would be used. Casingstring 500 may be positioned in well bore 510 with activation collars550 installed between sections of casing 140 at all connections ofsections of casing 540. Alternatively, activation collars 550 may beused at one or more selected locations in casing string 500 whichcorrespond to specific well bore locations in well bore 510 once theentire casing string 500 to be cemented is installed.

FIG. 6 a illustrates a cross-sectional view showing details of anexemplary activation collar 600, corresponding to the activation collars550 in FIG. 5, before operation. Activation collar 600 may include aninner housing member 610 coupled to sections of casing 620. Innerhousing member 610 may further include collar threading on one or moresurfaces of housing 610 as means of connecting to casing threading ofsections of casing 620. It should be understood by those skilled in theart that, in certain embodiments of the present disclosure, alternativemeans of connecting to sections of casing 620 may be employed.

Activation collar 600 may further include an outer housing member 630coupled to inner housing member 610. Outer housing member 630 may becoupled to inner housing member 610 by a threaded engagement that allowsrotational movement and causes the outer housing member 630 to moveaxially with respect to inner housing member 610. One of ordinary skillin the art, having the benefit of this disclosure, would understand thatalternative means of coupling outer housing member 630 to inner housingmember 610 may be employed.

A chemical reservoir 640 may be defined by inner housing member 610 andouter housing member 630. Chemical reservoir 640 may be any suitablemeans of containing one or more chemicals and/or activation agent.Activation collar 600 may be configured so that a relative rotationbetween inner housing member 610 and outer housing member 630 changesthe volume of chemical reservoir 640. One of ordinary skill in the art,having the benefit of this disclosure, would understand that alternativemeans of disposing a chemical reservoir between an inner housing and anouter housing of a collar may be employed so that the volume of thechemical reservoir may be reduced according to relative rotation betweenthe inner and outer housings.

Activation collar 600 may further include one or more outlets 650. Anoutlet 650 may be an open port between the chemical reservoir 640 andthe exterior of outer housing member 630. Outlet 650 may beappropriately sized such that the pressure balance of associated withthe exterior of outer housing member 630 prevents the activation agentfrom exiting the chemical reservoir 640 until the volume of chemicalreservoir 640 is decreased. Alternatively, outlet 650 may includeanother sealing element, such as a wax-like substance, to prevent theactivation agent from exiting the chemical reservoir 650 until chemicalreservoir 650 has been sufficiently compressed.

Activation collar 600 may further include one or more bowed springmembers-centralizer members 660. Centralizer members 660 may be coupledto outer housing member 630 to allow centralizer members 660 to contactsurfaces of the well bore when attached to a casing string downhole.Centralizer members 660 may accordingly provide resistance to rotationso that outer housing member 630 may tend to remain stationary. Inalternatives to a bowed spring member, those of ordinary skill in theart would appreciate that a centralizer member 660 may be of anothertype of projecting member designed to make contact with a surface of awell bore and may not necessarily be designed to provide a centralizingfunction.

After a non-activated cementitious material has been placed within alength of annulus 530, an operator may decide to “activate” thecementitious material to cause it to set, or otherwise release achemical into the annulus, by rotating casing string 500. Activationcollar 600 may be configured so that a predetermined number of rotationsof casing string 500 will actuate activation collar 600 and release anactivation agent. Casing string 500 may also be reciprocated axiallyalong well bore 500 to facilitate chemical dispersion. As casing string500 rotates, centralizer members 660 may make contact with surfaces ofthe well bore and hold outer housing member 630 stationary, therebyallowing relative rotation between casing string 500 and outer housingmember 630. A threaded engagement between outer housing member 630 andinner housing member 610 allows outer housing member 630 to move axiallywith respect to inner housing member 610. Chemical reservoir 640accordingly may be reduced in volume due to the axial relative movement,thereby causing an activation agent to be expelled from chemicalreservoir 640 into annulus 530.

FIG. 6 b illustrates a cross-sectional view showing details of exemplaryactivation collar 600 after outer housing member 630 has moved axiallywith respect to inner housing member 610. Outer housing member 630 andinner housing member 610 are shown as having compressed chemicalreservoir 640, and activation agent 670 that has been expelled throughoutlet 650 into the annulus. Concurrent or subsequent rotation and/orreciprocation of casing string 500 may distribute the activation agent670 within the fluid in the annulus. Activation collar 600 may also beconfigured to meter out activation agent 670 slowly while the casingstring is being rotated and/or reciprocated to facilitate distribution.Casing string 500 may then be positioned in its final desired locationbefore the activator causes the cementitious material to set.

FIG. 7 shows a process flow diagram for an exemplary activation collarrunning procedure 700. In step 710, activation collars may be installedon standard casing, or collars may be installed between standard casingjoints, prior to introducing a cementitious material into the well bore.In step 720, the casing string may be run into the well bore. In step730, the cement may be introduced into the well bore according tostandard procedures. In step 740, the casing string may be rotatedand/or reciprocated to release the activator and to mix the activatorwith the cement slurry. In step 750, the casing string may be placed andmaintained in its final position until cement hardening.

FIG. 8 illustrates a cross-sectional view showing details of anexemplary activation collar 800. Activation collar 800 corresponds toactivation collar 600, but alternatively may include one or morecentralizer members 810 at an angle with respect to a longitudinal axisof the casing string. Angling of centralizer members 810 may be used tominimize premature actuation of activation collar 800 when centralizermembers 810 are in contact with surfaces of the well bore. Theorientation and angle of centralizer members 810 may be configured to,in conjunction with surfaces of the well bore, bias outer housing member820 in the rotational direction that is opposite to the direction whichactuates activation collar 800. One of ordinary skill in the art, havingthe benefit of this disclosure, would understand that variousconfigurations of centralizer members 810 may be employed to optimizethe bias of outer housing member 820 and to minimize premature actuationof activation collar 800.

FIGS. 9 a and 9 b show details of another embodiment of the presentdisclosure. FIG. 9 a illustrates a cross-sectional view showing anexemplary activation collar 900 before activation agent 940 has beenexpressed through outlet 950 into the annulus. As an alternative to thethreaded engagement of activation collar 600, activation collar 900 mayinclude a j-slot or ratchet type release mechanism that may allowreciprocating motion to compress chemical reservoir 940, therebyexpressing one or more chemicals into the annulus. Activation collar 900may include an inner housing member 910 and an outer housing member 930coupled together at least in part by one or more lugs 970 and a j-slotpath 980.

For example, one or more lugs 670 may be attached to outer housingmember 930, and inner housing member 910 may include one or more j-slotpaths 980. Lug 970 may follow j-slot path 980 as the casing is moved upand down. J-slot path 980 may be configured so that, after a certainnumber of reciprocation cycles, lug 970 may follow a longer j-slot pathsection 990 which may allow relative motion between inner housing member910 and outer housing member 930 to sufficiently compress a volume ofchemical reservoir 940. FIG. 9 b illustrates activation collar 900 afterchemical reservoir 940 has been compressed and one or more chemicalshave been expressed through outlet 950 into the annulus.

Thus, in accordance with certain embodiments of the present disclosure,rotationally operated activation collars and methods are provided where“doses” of one or more chemicals and/or an activation agent may beintroduced at one or more points along a casing string, withoutproviding a potential leak path from the annulus to an interior diameterof the casing string. The casing string may be reciprocated and/orrotated to facilitate mixing an activation agent with a fluid in theannulus. Certain embodiments of this invention do not require externalor internal attachments to casing string for deployment of an activationagent. Certain embodiments allow for activator distribution within anentire cross-section of an annulus containing a cementitious material.The equipment and procedures for certain embodiments are not complex,require minimal modification to existing cementing procedures, and havelow operating risks.

FIGS. 10 a and 10 b shows another exemplary embodiment of the invention.FIG. 10 a illustrates straight blade centralizer 1000. FIG. 10 billustrates an axial view of straight blade centralizer 1000. Straightblade centralizer 1000 may be attached to the outside of a casing stringin the same manner that a conventional centralizer may be attached to acasing string according to standard practice in the oil and gasindustry. Straight blade centralizer 1000 may include one or morecollars 1010 that may be generally cylindrical or curved and designed towrap at least partially around a casing section.

Straight blade centralizer 1000 may further include a plurality ofhollow blades 1020 connected to the one or more collars 1010. Eachhollow blade 1020 may form a substantially complete enclosure of arounda hollow space. Alternatively, each hollow blade 1020 may form only apartially covered hollow space. For example, a hollow space may beexposed on the interior side of a hollow blade 1020 (i.e., the sideclosest the longitudinal axis of straight blade centralizer 1000).

FIG. 11 illustrates a cross-sectional view showing straight bladecentralizer 1100, which corresponds to straight blade centralizer 1000of FIGS. 10 a and 10 b, coupled to casing 1110. Straight bladecentralizer 1100 may include one or more collars 1120 and one or morehollow blades 1130. FIG. 11 depicts two hollow blades 1130, although adifferent number of hollow blades 1130 may be used. Each hollow blade1130 may house or cover, at least in part, a chemical container 1140such as a canister filled with one or more chemicals to be dispensedinto the annulus. Chemical containers 1140 may be held inside of hollowblades 1130, or otherwise disposed near an interior surface of hollowblades 1130, as the casing string is lowered into the well bore. Thisallows chemical containers 1140 to be protected when in the well bore.

The chemical containers or reservoirs may be made of any material suchas steel, aluminum, brass, glass, plastic, lead, wood, ceramic orflexible bags. Each chemical container may be pressure balanced with amechanism known in the art so that the pressure associated with deepwell bores will not cause the chemical container to collapse. In thecase where the chemical container may include a flexible bag, thechemical container may be inherently pressure balanced by virtue of itsflexible design. In certain embodiments, a hollow blade 1130 may itselfbe the chemical container.

In certain embodiments, each chemical container 1140 may be equippedwith a pump 1150 that may be remotely activated to release one or morechemicals at any arbitrary moment. It is to be understood that pump 1150may be or include a pump, a valve, or any device configured to express,eject, pump, transfer, or otherwise release the chemicals. Pump 1150 maybe activated by pressure or pressure pulse from the surface down theannulus. In the alternative, pump 1150 may be activated by lowering adevice on slick line or wireline into the interior of the casing thatwould signal each valve to release chemicals from the chemical containerinto the annulus as the device passes nearby. This signal could be inthe form of acoustic, radioactive, neutron, magnetic, thermal or anyother type of signal that would penetrate the steel casing for a shortdistance. One of ordinary skill in the art, having the benefit of thisdisclosure, would understand that various configurations could beemployed to activate pump 1150. Thus, in accordance with certainembodiments, chemicals in chemical containers 1140 may be dispensed atany point in time.

FIG. 12 illustrates a cross-sectional view showing additionalembodiments, where centralizer 1200 may include elements of straightblade centralizer 1100 as well as elements of a bow spring centralizer.Centralizer 1200 may include one or more collars 1210 may be generallycylindrical or curved and designed to wrap at least partially around acasing section 1220. Bowed spring members 1230 may be attached tocollars 1210 to allow bowed spring members 1230 to contact surfaces ofthe well bore when attached to a casing string downhole. Although twobowed spring members are depicted in the example of FIG. 12, it shouldbe understood that certain embodiments may employ one or a differentnumber of bowed spring members. Bowed spring members 1230 mayaccordingly provide resistance to rotation so that all or part ofcentralizer 1200 may tend to remain stationary. Collars 1210 may beslidably coupled to casing section 1220 in order to slide freely andallow bowed spring members 1230 to flex when in contact with walls ofthe well bore. Collars 1210 may be configured to move away from eachother to allow such flexure of bowed spring members 1230. One or morehollow blades 1240 may be connected or otherwise coupled to one or theother of collars 1210 so as not to inhibit flexure of bowed springmembers 1230. One of ordinary skill in the art, with the benefit of thisdisclosure, would appreciate that various alternative means of couplingcentralizer 1200 to a casing section may be employed. Moreover, in thealternative to a bowed spring member, those of ordinary skill in the artwould appreciate that a centralizer 1200 may include one or more ofanother type of projecting member designed to make contact with asurface of a well bore and may not necessarily be designed to provide acentralizing function.

As with the straight blade centralizer 1000 in FIG. 10, each hollowblade 1240 of centralizer 1200 may form a substantially completeenclosure of around a hollow space. Alternatively, each hollow blade1240 may form only a partially covered hollow space where, for example,the hollow space may be exposed on the interior side (i.e., the “casingside”) of a hollow blade 1240. FIG. 12 depicts two hollow blades 1240,although a different number of hollow blades 1240 may be used. As withthe straight blade centralizer 1000 in FIG. 10, each hollow blade 1240of centralizer 1200 may house or cover, at least in part, a chemicalcontainer 1250 such as a canister filled with one or more chemicals tobe dispensed into the annulus. Chemical containers 1250 may be heldinside of hollow blades 1240, or otherwise disposed near an interiorsurface of hollow blades 1240, as the casing string is lowered into thewell bore.

In certain embodiments, each chemical container 1250 may be equippedwith a pump 1260. Pump 1260 may be linked to the casing 1220 in a mannerknown in the art so that, when casing 1220 is rotated, pump 1260 may beforced open to thereby release one or more chemicals from chemicalcontainer 1250, and/or forced to actively express the chemicals fromchemical container 1250. In other embodiments, pump 1260 may bealternatively configured for activation with the approaches discussedabove with respect to FIG. 11.

In certain alternative embodiments where chemical container 1250 mayinclude a plastic or a flexible bag, a cutting instrument 1270, such asa knife edge, may be coupled to casing 1220 in a manner known in theart. When casing 1220 is rotated, each plastic container or bag may becut open, thereby releasing the chemical. One of ordinary skill in theart, with the benefit of this disclosure, would appreciate that variousalternative means of releasing chemicals from chemical container 1250may be employed. For example, cutting instrument 1270 may include anymeans that would cut, tear, lacerate, puncture, penetrate, snag, tear,unseal, or otherwise release one or more chemicals from chemicalcontainer 1250.

FIG. 13 shows a cross-sectional view illustrating an additionalembodiment, where activation collar 1300 may correspond to activationcollar 1200, for example, but be configured to include distributiontubes 1310. Distribution tubes 1310 may be coupled to an outlet 1320 ofthe chemical containers so an activator chemical may be distributedfurther from an initial point of release. Distribution tubes 1310 may beattached to the casing by straps, clamps, welding or other means aswould be understood by one of ordinary skill in the art. Distributiontubes 1310 may include one or more outlets to express the chemical. Forexample, distribution tube 1310 may be perforated and may be designed torelease the chemical in a manner similar to the function of a soakerhose sometimes used in gardening. Distribution tubes 1310 tubes may beof any length desired and may be spiraled around the outside of thecasing. Activation collar 1300 may accordingly facilitate activatinglonger sections of the cement in the annulus.

Thus, in accordance with certain embodiments of the present disclosure,one or more chemicals and/or activating agents may be released into thewell bore “on command.” The chemicals may be left stagnant and allowedto disperse into the surrounding fluid in the annulus by means ofdiffusion, or the chemicals may be mixed into the annular fluid byreciprocating or rotating the casing for a period of time as discussedabove. As would be appreciated by one of ordinary skill in the art, theblades of the centralizer would provide a means to stir the fluid andmix the chemical in with it. Certain embodiments allow for activatordistribution within an entire cross-section of an annulus containing acementitious material. The equipment and procedures for certainembodiments are not complex, require minimal modification to existingcementing procedures, and have low operating risks.

Therefore, the present disclosure is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent disclosure may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered ormodified and all such variations are considered within the scope andspirit of the present disclosure. Also, the terms in the claims havetheir plain, ordinary meaning unless otherwise explicitly and clearlydefined by the patentee.

1. An apparatus for releasing a chemical in a well bore, the apparatuscomprising: a casing collar configured to connect to a section of acasing string; and a chemical reservoir disposed between an interiorsurface and an exterior surface of the casing collar; wherein the casingcollar is configured to release a chemical from the chemical reservoir;wherein the chemical comprises an activation agent; and wherein thecasing collar comprises an inner casing collar member and an outercasing collar member, wherein the inner casing collar member and theouter casing collar member are configured to compress the chemicalreservoir in response to movement of the inner casing collar memberrelative to the outer casing collar member.
 2. The apparatus of claim 1,wherein the casing collar is configured to release the chemical from thechemical reservoir in response to an increase of pressure on an interiorsurface of the casing string.
 3. The apparatus of claim 2, wherein thecasing collar comprises a rupture element.
 4. The apparatus of claim 2,wherein the casing collar comprises a tension element.
 5. The apparatusof claim 2, wherein the casing collar comprises a piston configured tocompress the chemical reservoir.
 6. The apparatus of claim 1, whereinthe movement comprises rotation of the casing collar relative to thesection.
 7. The apparatus of claim 1, wherein the outer collar member iscoupled to the inner casing collar member with a slot assembly, whereinthe slot assembly comprises a j-slot and a lug configured to move withinthe j-slot.
 8. The apparatus of claim 1, wherein the casing collarcomprises a projecting member configured to extend further from an axisof the casing string than the outer collar member.
 9. A method forreleasing a chemical in a well bore, comprising the steps of: connectingan activator collar between sections of a casing string, the activatorcollar being generally cylindrical and comprising an interior surface,an exterior surface, and a chemical reservoir disposed therebetween;positioning the activator collar and the sections in a well bore;introducing a non-activated cementitious material into the well bore;and releasing a chemical from the activator collar into the well bore.10. The method of claim 9, wherein the releasing of the chemical isinitiated by increasing pressure on an interior surface of the casingstring.
 11. The method of claim 9, wherein the releasing of the chemicalis initiated by movement of the casing string.